Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$74.34	9.219%	$81.1934	$81.19	$81.20	$81.20
Purchase #2	$188.92	5.190%	$198.7249	$198.72	$198.70	$198.70
Purchase #3	$126.61	13.619%	$143.853	$143.85	$143.85	$143.90
Purchase #4	$156.48	6.430%	$166.5417	$166.54	$166.55	$166.50
Purchase #5	$206.64	12.816%	$233.123	$233.12	$233.10	$233.10
Purchase #6	$115.43	3.811%	$119.829	$119.83	$119.85	$119.80
Purchase #7	$126.62	3.628%	$131.2138	$131.21	$131.20	$131.20
7 purchase totals =	$995.04		$1,074.4788	$1,074.46	$1,074.45	$1,074.40